Just drafted a basket of parts for a intermediate shaft to ease the implementation of large transmission rates.
The example was chosen to resemble the ratio "1:2,3:3" as mentioned in the QS 138 description for the alibaba package.
I assume 10T at the motor and 42T at the back wheel.
(EP is single price in €, GP is total price, excl VAT, kg is weight single/total)
The choice may not be perfect, just to give a rough idea.
I went for taper lock system as they are the easiest to fix without special milling.
May not be perfect choice to omptimize weight.
Unfortunately, the 20mm-6 teeth splined shaft does not match the profile of the chinese sprockets as on the QS motor.
Those are 17,75 inner dia and 4mm tooth (coursely calipered) with, while the maedler shaft ist 16 mm inner dia and 6mm teeth.
Of course you have to account for the addional effort, weight, cost and place required to support this intermediate shaft.
Personally, I'd still prefer the simplier solution with a large rear sprocket.
mh... hang on .... , I know that with large sprockets, even moderate chain wear causes the chain to climb. hmm....
